1. Field of the Invention
The present invention relates to image-reading devices used in facsimiles and copiers, and to image-forming apparatuses having same.
2. Description of the Related Art
It is known to provide internal-output type image-forming apparatus, such as facsimiles and copiers, which have an image-forming section in the central portion of the main body thereof and an image-reading section at the uppermost portion thereof. A sheet that is provided with an image is moved to a space between the image-forming section and the image-reading section.
Because of its structure, such an internal-output type image-forming apparatus tends to be tall. To reduce the height of the apparatus, a reduction in the thickness of the image-reading section is required. However, because of a rotation moment generated at a hinge where the image-reading section is fixed when the document conveying portion is opened and closed, the image-reading section is subjected to a large load due to the rotation moment. This can distort or deform the image-reading section. If the image-reading section is distorted or deformed, the positional relationship between the scanning unit and the optical unit that is located in the image-reading section can be affected, adversely affecting the image-reading performance. Thus, the structure of the image-reading section itself needs to be strengthened so as not to be distorted or deformed. This, however, not only prevents reducing the thickness and weight of the image-reading section, but also is disadvantageous from the standpoint of costs.
Consequently, a method for reducing the load applied to the image-reading section due to a rotation moment about the hinge to thereby enable a reduction in the thickness of the image-reading section has been proposed. Japanese Unexamined Patent Application Publication No. 2003-51906 discloses an image-forming apparatus in which a load applied to the image-reading section is reduced by fixing the hinge unit to a post connecting the image-reading section and the image-forming section thereby distributing the load, generated by the rotation moment, to the post.
Furthermore, Japanese Unexamined Patent Application Publication No. 2005-130347 discloses a method for reducing a load applied to the image-reading section due to the rotation moment by providing an embossed portion at least a part of a frame of the image-reading device.
However, with the method disclosed in Japanese Unexamined Patent Application Publication No. 2003-51906, because the hinge unit is fixed to the post of the image-reading section, the rotation moment about the hinge unit is, to some extent, transmitted to the image-reading section via the post. Thus, it is difficult to completely prevent the load from being applied to the image-reading section and to assure the prevention of the deformation of the image-reading section. Furthermore, the weight of the document conveying unit varies depending on the model, and because, for example, an image-forming apparatus capable of high-speed processing can hold a large number of documents, the size and weight of the document conveying unit is large. Accordingly, it is assumed that the load applied to the image-reading section via the post is also large.
With the method disclosed in Japanese Unexamined Patent Application Publication No. 2005-130347 too, although the embossed portion enhances the rigidity of the frame, it is difficult to completely prevent deformation of the rear side surface to which the hinge unit is attached, due to the opening and closing of the document conveying unit. There is also a problem in that, because the rear side surface usually has a guide rail for moving a carriage that carries a lamp and a mirror, a deformation of the rear side surface also causes a deformation of the guide rail. This can adversely affect the image-reading accuracy. Although image-reading devices having the document conveying units have been described herein, image-reading devices having only document holding plates also, more or less, have the same problem.